Join implementation changes

...client/gms-cli/src/main/java/it/inaf/ia2/gms/cli/CLI.java

...t-lib/src/main/java/it/inaf/ia2/gms/client/GmsClient.java

...b/src/test/java/it/inaf/ia2/gms/client/GmsClientTest.java

gms/src/main/java/it/inaf/ia2/gms/GmsApplication.java

gms/src/main/java/it/inaf/ia2/gms/authn/JWTFilter.java

gms/src/main/java/it/inaf/ia2/gms/authn/RapPrincipal.java

...naf/ia2/gms/controller/BasicAuthWebServiceController.java

...a/it/inaf/ia2/gms/controller/JWTWebServiceController.java

...main/java/it/inaf/ia2/gms/model/PrepareToJoinRequest.java

gms/src/main/java/it/inaf/ia2/gms/persistence/JoinDAO.java

...main/java/it/inaf/ia2/gms/persistence/MembershipsDAO.java

...main/java/it/inaf/ia2/gms/persistence/PermissionsDAO.java

...a/it/inaf/ia2/gms/persistence/model/MembershipEntity.java

...a/it/inaf/ia2/gms/persistence/model/PermissionEntity.java

gms/src/main/java/it/inaf/ia2/gms/service/JoinService.java

...src/main/java/it/inaf/ia2/gms/service/MembersService.java

...main/java/it/inaf/ia2/gms/service/PermissionsService.java

gms/src/main/resources/application.properties

...ia2/gms/controller/BasicAuthWebServiceControllerTest.java

.../test/java/it/inaf/ia2/gms/persistence/GroupsDAOTest.java